FAST APPROXIMATE MATCHING OF WORDS AGAINST A DICTIONARY

A new algorithm for string edit distance computation is given. The algorithm assumes that one of the two strings to be compared is a dictionary entry that is known a priori. This dictionary word is converted in an off-line phase into a deterministic finite state automaton. Given an input string and the automaton derived from the dictionary word, the computation of the edit distance between the two strings corresponds to a traversal of the states of the automaton. This procedure needs time which is only linear in the length of the input string. It is independent of the length of the dictionary word. Given not only one but N different dictionary words, their corresponding automata can be combined into a single deterministic finite state automaton. Thus the computation of the edit distance between the input word and each dictionary entry, and the determination of the nearest neighbor in the dictionary need time that is only linear in the length of the input string. However, the number os states of the automaton is exponential.